qemu_migration: Apply max-postcopy-bandwidth on post-copy resume

When resuming post-copy migration users may want to limit the bandwidth
used by the migration and use a value that is different from the one
specified when the migration was originally started.

Resolves: https://gitlab.com/libvirt/libvirt/-/issues/333

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

src/qemu/qemu_migration.c

@@ -5051,12 +5051,13 @@ qemuMigrationSrcRun(virQEMUDriver *driver,
 
 static int
 qemuMigrationSrcResume(virDomainObj *vm,
-                       qemuMigrationParams *migParams G_GNUC_UNUSED,
+                       qemuMigrationParams *migParams,
                        const char *cookiein,
                        int cookieinlen,
                        char **cookieout,
                        int *cookieoutlen,
-                       qemuMigrationSpec *spec)
+                       qemuMigrationSpec *spec,
+                       unsigned long flags)
 {
     qemuDomainObjPrivate *priv = vm->privateData;
     virQEMUDriver *driver = priv->driver;
@@ -5073,6 +5074,10 @@ qemuMigrationSrcResume(virDomainObj *vm,
     if (!mig)
         return -1;
 
+    if (qemuMigrationParamsApply(driver, vm, VIR_ASYNC_JOB_MIGRATION_OUT,
+                                 migParams, flags) < 0)
+        return -1;
+
     if (qemuDomainObjEnterMonitorAsync(driver, vm,
                                        VIR_ASYNC_JOB_MIGRATION_OUT) < 0)
         return -1;
@@ -5154,6 +5159,7 @@ qemuMigrationSrcPerformNative(virQEMUDriver *driver,
 
     if (STREQ(uribits->scheme, "unix")) {
         if ((flags & VIR_MIGRATE_TLS) &&
+            !(flags & VIR_MIGRATE_POSTCOPY_RESUME) &&
             !qemuMigrationParamsTLSHostnameIsSet(migParams)) {
             virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
                            _("Explicit destination hostname is required "
@@ -5185,7 +5191,7 @@ qemuMigrationSrcPerformNative(virQEMUDriver *driver,
 
     if (flags & VIR_MIGRATE_POSTCOPY_RESUME) {
         ret = qemuMigrationSrcResume(vm, migParams, cookiein, cookieinlen,
-                                     cookieout, cookieoutlen, &spec);
+                                     cookieout, cookieoutlen, &spec, flags);
     } else {
         ret = qemuMigrationSrcRun(driver, vm, persist_xml, cookiein, cookieinlen,
                                   cookieout, cookieoutlen, flags, resource,

src/qemu/qemu_migration_params.c

@@ -141,6 +141,7 @@ struct _qemuMigrationParamsTPMapItem {
 typedef struct _qemuMigrationParamInfoItem qemuMigrationParamInfoItem;
 struct _qemuMigrationParamInfoItem {
     qemuMigrationParamType type;
+    bool applyOnPostcopyResume;
 };
 
 /* Migration capabilities which should always be enabled as long as they
@@ -265,6 +266,7 @@ static const qemuMigrationParamInfoItem qemuMigrationParamInfo[] = {
     },
     [QEMU_MIGRATION_PARAM_MAX_POSTCOPY_BANDWIDTH] = {
         .type = QEMU_MIGRATION_PARAM_TYPE_ULL,
+        .applyOnPostcopyResume = true,
     },
     [QEMU_MIGRATION_PARAM_MULTIFD_CHANNELS] = {
         .type = QEMU_MIGRATION_PARAM_TYPE_INT,
@@ -782,7 +784,8 @@ qemuMigrationParamsFromJSON(virJSONValue *params)
 
 
 virJSONValue *
-qemuMigrationParamsToJSON(qemuMigrationParams *migParams)
+qemuMigrationParamsToJSON(qemuMigrationParams *migParams,
+                          bool postcopyResume)
 {
     g_autoptr(virJSONValue) params = virJSONValueNewObject();
     size_t i;
@@ -795,6 +798,9 @@ qemuMigrationParamsToJSON(qemuMigrationParams *migParams)
         if (!pv->set)
             continue;
 
+        if (postcopyResume && !qemuMigrationParamInfo[i].applyOnPostcopyResume)
+            continue;
+
         switch (qemuMigrationParamInfo[i].type) {
         case QEMU_MIGRATION_PARAM_TYPE_INT:
             rc = virJSONValueObjectAppendNumberInt(params, name, pv->value.i);
@@ -868,6 +874,7 @@ qemuMigrationCapsToJSON(virBitmap *caps,
  *
  * Send parameters stored in @migParams to QEMU. If @apiFlags is non-zero, some
  * parameters that do not make sense for the enabled flags will be ignored.
+ * VIR_MIGRATE_POSTCOPY_RESUME is the only flag checked currently.
  *
  * Returns 0 on success, -1 on failure.
  */
@@ -876,32 +883,38 @@ qemuMigrationParamsApply(virQEMUDriver *driver,
                          virDomainObj *vm,
                          int asyncJob,
                          qemuMigrationParams *migParams,
-                         unsigned long apiFlags G_GNUC_UNUSED)
+                         unsigned long apiFlags)
 {
     qemuDomainObjPrivate *priv = vm->privateData;
     bool xbzrleCacheSize_old = false;
     g_autoptr(virJSONValue) params = NULL;
     g_autoptr(virJSONValue) caps = NULL;
     qemuMigrationParam xbzrle = QEMU_MIGRATION_PARAM_XBZRLE_CACHE_SIZE;
+    bool postcopyResume = !!(apiFlags & VIR_MIGRATE_POSTCOPY_RESUME);
     int ret = -1;
 
     if (qemuDomainObjEnterMonitorAsync(driver, vm, asyncJob) < 0)
         return -1;
 
-    if (asyncJob == VIR_ASYNC_JOB_NONE) {
+    /* Changing capabilities is only allowed before migration starts, we need
-        if (!virBitmapIsAllClear(migParams->caps)) {
+     * to skip them when resuming post-copy migration.
-            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+     */
-                           _("Migration capabilities can only be set by "
+    if (!postcopyResume) {
-                             "a migration job"));
+        if (asyncJob == VIR_ASYNC_JOB_NONE) {
-            goto cleanup;
+            if (!virBitmapIsAllClear(migParams->caps)) {
-        }
+                virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
-    } else {
+                               _("Migration capabilities can only be set by "
-        if (!(caps = qemuMigrationCapsToJSON(priv->migrationCaps, migParams->caps)))
+                                 "a migration job"));
-            goto cleanup;
+                goto cleanup;
+            }
+        } else {
+            if (!(caps = qemuMigrationCapsToJSON(priv->migrationCaps, migParams->caps)))
+                goto cleanup;
 
-        if (virJSONValueArraySize(caps) > 0 &&
+            if (virJSONValueArraySize(caps) > 0 &&
-            qemuMonitorSetMigrationCapabilities(priv->mon, &caps) < 0)
+                qemuMonitorSetMigrationCapabilities(priv->mon, &caps) < 0)
-            goto cleanup;
+                goto cleanup;
+        }
     }
 
     /* If QEMU is too old to support xbzrle-cache-size migration parameter,
@@ -917,7 +930,7 @@ qemuMigrationParamsApply(virQEMUDriver *driver,
         migParams->params[xbzrle].set = false;
     }
 
-    if (!(params = qemuMigrationParamsToJSON(migParams)))
+    if (!(params = qemuMigrationParamsToJSON(migParams, postcopyResume)))
         goto cleanup;
 
     if (virJSONValueObjectKeysNumber(params) > 0 &&

src/qemu/qemu_migration_paramspriv.h

@@ -26,7 +26,8 @@
 #pragma once
 
 virJSONValue *
-qemuMigrationParamsToJSON(qemuMigrationParams *migParams);
+qemuMigrationParamsToJSON(qemuMigrationParams *migParams,
+                          bool postcopyResume);
 
 qemuMigrationParams *
 qemuMigrationParamsFromJSON(virJSONValue *params);

tests/qemumigparamstest.c

@@ -155,7 +155,7 @@ qemuMigParamsTestJSON(const void *opaque)
     if (!(migParams = qemuMigrationParamsFromJSON(paramsIn)))
         return -1;
 
-    if (!(paramsOut = qemuMigrationParamsToJSON(migParams)) ||
+    if (!(paramsOut = qemuMigrationParamsToJSON(migParams, false)) ||
         !(actualJSON = virJSONValueToString(paramsOut, true)))
         return -1;
 

tests/qemumigrationcookiexmltest.c

@@ -333,7 +333,7 @@ testQemuMigrationCookieBlockDirtyBitmaps(const void *opaque)
 
     qemuMigrationParamsSetBlockDirtyBitmapMapping(migParams, &migParamsBitmaps);
 
-    if (!(paramsOut = qemuMigrationParamsToJSON(migParams)) ||
+    if (!(paramsOut = qemuMigrationParamsToJSON(migParams, false)) ||
         !(actualJSON = virJSONValueToString(paramsOut, true)))
         return -1;